CAPI Heider is the Heider preamp line from Classic Audio Products, Inc. (CAPI), a hand-built pro audio company based in Nashville, Tennessee, founded by Jeff Steiger. The Heider modules recreate the sound of the custom mic preamps in Wally Heider Recording Studio 4, a console built by Frank DeMedio circa 1972 that swapped the standard AP2622 input transformer for a custom-wound Ed Reichenbach RE-0887, prized for its midrange character.

The line consists of 500-series microphone preamps. The original FD312 was followed roughly a decade later by the FD312 H2 revision, which introduced a CAPI-exclusive version of the RE-0887 input transformer, Litz-wire 2503 output transformers shared with CAPI's Platinum line, potted CA-0252 discrete opamps, and an 80Hz high-pass filter in place of the original impedance load switch. A limited "CAPIRRUNE" variant of the H2, made in a run of 50 units in collaboration with Colt Capperrune, features a black-on-black faceplate and custom hardware.

Each Heider unit is hand assembled, burned in and tested at CAPI's Nashville facility. The preamps are sold direct through capi-gear.com and through pro audio dealers including Resistance Audio, ZenPro Audio, and Atlas Pro Audio.

CAPI Heider has 4 products cataloged on Equipboard, including Preamps. Their gear is featured by 1 artist, with the strongest followings in Pop. Notable users include Colt Capperrune.